Having an account at apple grow I can do the updates of the software beta versions for the Apple TV.
Surprise I have ever been able to do an update because of an "error 40" I do not remember exactly the error number ... changing micro usb cable with another which is m ' lent I have not had an error. I could take the test several times without success!
The cable diameter should be involved ... If you know of cables compatible with the apple tv I'm interested (in the meantime I have a micro usb cable to a mobile phone :))
A priori seen other reviews there are several kinds of cables that are sent ... to haphazardly. I have not complain considering the price but it is not very correct from the seller.